1. Field of the Invention
The present invention relates to a force assisting device capable of moving an appliance having a heavy weight through assistance of an actuator by only application of small force by an operator. More particularly, the present invention relates to a method of controlling a force assisting device which is suitable to support a microscope for surgical operation movable by small force and a control apparatus using this device.
2. Related art
A force assisting device is a device for supporting a heavy object so as to be easily movable by an old person or even a common person in a manner of amplifying small force by the operator. For example, in a medical field, a doctor uses a microscope in order to observe an affected part extensively during surgical operation. The microscope, if it is large scaled, is supported by a force assisting device so that it can be moved by small force.
Examples of this force assisting device are to support the microscope by a balancer such as a weight or spring so that it can be moved by small force, and to'support the microscope by a balancer and also shift or rotate the microscope in a prescribed direction by operating a joystic or switch using an electric or hydraulic motor as a power source (e.g. Japanese Patent Publn. 5-3304).
However, the above force assisting device which moves the microscope by the balancer is poor in operability because the weight balance varies according to changes in the position and orientation of the microscope or replacement of the microscope and hence the operation force that an operator needs also varies.
Since balance adjustment is complicated, the maintenance is troublesome. The above force assisting device using the balancer cannot perform a "point lock operation" of moving an environment so as to change the observation perspective of a focal point with the focal point of the microscope being fixed (making the environment movable or rotatable along a prescribed track).
The force assisting device which shifts or rotates the microscope in a prescribed direction by operating a joystic or switch is also poor since the microscope can be shifted or moved only in a prescribed direction. When the microscope is moved by the on/off operation of the joystick or switch, it performs a clumsy operation such as abrupt start or stop so that a sense of a smooth operation cannot be obtained.